Super-hydrophobic fiber having needle-shaped nano structure on its surface, method for fabricating the same and fiber product comprising the same

ABSTRACT

A super-hydrophobic fiber of the present disclosure includes: a nano-needle fiber having a surface including needle-shaped nano structures; and a coating layer disposed on the surface including the nano structures, and containing a hydrophobic material. The fiber has no aging effect, and thus, is excellent in durability, and has such a large contact angle and such as small sliding angle that the fiber may not be wet with water. A method for fabricating the super-hydrophobic fiber includes: a preparation step of preparing a pre-treating fiber; an etching step of etching a surface and an inner portion of the pre-treating fiber to fabricate a nano-needle fiber having a surface on which needle-shaped nano structures are formed; and a coating step of forming a coating layer containing a hydrophobic material, and enables mass production and is performed by simple processes. 
     Further, an article including the super-hydrophobic fiber is an article in which no liquid drop is absorbed, scarcely adsorbs a contaminant, needs not be dried, and thus, may be widely applied even to recreational articles.

CROSS-REFERENCE TO RELATED APPLICAION

Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2014-0000891, filed on Jan. 3, 2014, the contents of which is incorporated by reference herein in its entirety.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates to super-hydrophobic fiber having a surface including needle-shaped nano structures and in which a coating layer containing a hydrophobic material is formed on the surface, a method for fabricating the same, and a fiber product comprising the same.

2. Background of the Disclosure

In order to impart a hydrophobic or contamination prevention function to the conventional functional clothing, methods of coating a material having a low surface energy, such as hydrophobic Teflon have been adopted. Further, International Publication No. WO 2012/152997 discloses a method of forming a super-hydrophobic surface having a nano structure including: applying a solution obtained by mixing nanocellulose particles on the surface by a spray method, and evaporating moisture from the applied solution, but since a hydrophobic solution is applied by a spray method, it is difficult to form a uniform coating layer, and there is a problem in that due to the separation of particles introduced for forming a hydrophobic surface from the surface, contamination, or deterioration in hydrophobic characteristics easily occurs.

As another example, the document [M. Joshi, et al., Nano structured coatings for super hydrophobic textiles, Bulletin of Materials Science] suggests a method of forming a surface with a low surface energy having a nano structure by depositing silica nanoparticles on fabric, but since there is a concern in that the particles may be subsequently desorbed due to using a method of depositing particles, there is a limitation in durability, and there is a problem in that contamination caused by particle dust may occur or performance may deteriorate.

As described above, in the case of a method of directly depositing the nano structure on fiber such as fabric, the deposited material is desorbed, or the coating layer is easily worn due to weak durability, and as a result, the performance may rapidly deteriorates, and contamination and the like due to desorbed particles may lead to problems.

In addition, these methods may have environmental contamination due to waste water by using solutions and the like in the fabrication process, and also have problems in that the process is complicated, process costs are increased, and it is a little difficult to achieve mass production.

SUMMARY OF THE DISCLOSURE

Therefore, an aspect of the detailed description is to provide super-hydrophobic fiber in which super-hydrophobicity, which does not make the surface wet, is maintained without aging effects for a long period of time by imparting durable super-hydrophobicity to the surface of fiber (or fabric) such as polyester, a method for fabricating the same, and a fiber product comprising the same. The fabricating method has environmentally-friendly production processes, is inexpensive in terms of fabrication costs and may be applied to fibers, fabrics and the like made of various materials, and may also be applied to commercialized fibers.

The super-hydrophobic fiber according to an exemplary embodiment of the present disclosure includes: a nano-needle fiber having a surface including needle-shaped nano structures; and a coating layer disposed on the surface including the needle-shaped nano structures and containing a hydrophobic material.

The needle-shaped nano structure may have a height of 50 to 150 nm and a width of 5 to 20 nm, and the surface including the needle-shaped nano structures may include 2 million to 4 million needle-shaped nano structures per 1 mm² of an area.

The needle-shaped nano structures may be formed on the outermost surface of a pre-treating fiber and at the inner surface portion which is up to 100 μm deep from the outermost surface.

The super-hydrophobic fiber may be one material selected from the group consisting of polyester, polyurethane, polyamide, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, acrylonitrile, polypropylene, polyacryl, and a combination thereof.

The coating layer may have a thickness of 5 to 100 nm, and the hydrophobic material may be one selected from the group consisting of hexamethyldisiloxane (HMDSO), molybdenum disulfide (MoS₂), boron nitride (BN), polytetra fluoroethylene (PTFE), fluorinated diamond like carbon (F-DLC), and a combination thereof.

The super-hydrophobic fiber may have a contact angle of 150 degree or more with pure water, and a sliding angle of 3 degree or less with pure water.

A method for fabricating super-hydrophobic fiber according to another exemplary embodiment of the present disclosure includes: a preparation step of preparing a pre-treating fiber to be subjected to super-hydrophobic treatment; an etching step of etching an outermost surface of the pre-treating fiber and an inner surface portion which is 100 μm deep from the outermost surface to fabricate a nano-needle fiber having a surface on which needle-shaped nano structures are formed; and a coating step of forming a coating layer containing a hydrophobic material on the surface on which nano structures of the fiber are formed.

The etching step may be one method selected from the group consisting of plasma etching, reactive ion etching, ion-milling, electro discharge machining (EDM), and a combination thereof.

The plasma etching may be performed for 30 sec to 90 min while a reactive gas is included, and the reactive gas may be one selected from the group consisting of CF₄, CHF₃, C₂F₆, C₂Cl₂F₄, C₃F₈, C₄F₈, SF₆, O₂, and a mixture thereof, and the plasma etching may be performed under conditions of a pressure of 10 to 100 mTorr, an rf-power of 100 to 400 W, and a bias voltage of 300 to 500 V for 5 min to 40 min.

In the coating step, a coating layer containing a hydrophobic material may be formed by one selected from the group consisting of plasma enhanced chemical vapor deposition (PECVD), atmospheric chemical vapor deposition (APCVD), low pressure chemical vapor deposition (LPCVD), metal-organic chemical vapor deposition (MOCVD), ultra-high vacuum chemical vapor deposition (UHCVD), atomic layer deposition (ALD), and a combination thereof.

The coating step may be performed by plasma enhanced chemical vapor deposition (PECVD), and may be performed under conditions of a pressure of 5 to 30 mTorr, an rf-power of 150 to 400 W, and a bias voltage of 300 to 500 V.

The needle-shaped nano structure may have a height of 50 to 150 nm and a width of 5 to 20 nm, and may include 2 million to 4 million needles per 1 mm² of a surface area of the fiber.

The fiber may be one selected from the group consisting of polyester, polyurethane, polyamide, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, acrylonitrile, polypropylene, polyacryl, and a combination thereof.

The hydrophobic material may be one selected from the group consisting of hexamethyldisiloxane (HMDSO), molybdenum disulfide (MoS₂), boron nitride (BN), polytetra fluoroethylene (PTFE), fluorinated diamond like carbon (F-DLC), and a combination thereof.

A fiber product according to still another exemplary embodiment of the present disclosure includes: a nano-needle fiber having a surface including needle-shaped nano structures; and a coating layer disposed on the surface including needle-shaped nanostructures, and containing a hydrophobic material.

The needle-shaped nano structure have a height of 50 to 150 nm and a width of 5 to 20 nm, the surface may include 2 million to 4 million needle-shaped nano structures per 1 mm² of an area, and the fiber product may be one selected from the group consisting of a tent, an umbrella, shoes, a banner, a cap, a bag, a knapsack, and clothes.

As used herein, the term “include” or “have” indicates that a feature, a number, a step, a component, and a combination thereof described in the specification is present, but do not exclude the possibility of presence or addition of one or more other features, numbers, steps, components, and combinations thereof, in advance.

As used herein, the term “needle-shaped” or “nano needle” is a term that expresses a nano structure in the form of a nanoscale needle, and expresses a nano structural body formed on the surface of a material. The shape of the nano structure may be a polyprism, a polypyramid, a circular cylinder, a circular cone, and the like, and may also be a structural body having different areas of the bottom surface and the top surface.

Singular or plural expressions used in the present specification do not limit the number in a specific material, and may refer to one specific material, or may refer to a group formed of a specific material. As used herein, the term “pre-treating fiber” is a fiber in the raw material state before being subjected to super-hydrophobic treatment and refers to a fiber before being etched, and the term “nano-needle fiber” refers to a fiber which has a surface including a needle-shaped nano structure by forming the needle-shaped nano structure on the surface of a pre-treating fiber through the etching step.

Unless otherwise defined herein, the term “fiber” as used herein is used as a meaning including not only a type of fiber in the form of yarn, but also a type of fiber included in a raw fabric having a texture structure such as fabric, knit and unwoven fabric.

Hereinafter, the present disclosure will be described in more detail.

The super-hydrophobic fiber according to an exemplary embodiment of the present disclosure includes: a nano-needle fiber having a surface including needle-shaped nano structures; and a coating layer disposed on the surface including the needle-shaped nano structure and containing a hydrophobic material.

The needle-shaped nano structure may have a height of 50 to 150 nm and a width of 5 to 20 nm, and the surface including the needle-shaped nano structures may include 2 million to 4 million needle-shaped nano structures per 1 mm² of an area.

The needle-shaped nano structures may be formed on the outermost surface of a pre-treating fiber and at the inner surface portion which is 100 μm, preferably 150 μm, and more preferably 200 μm deep from the outermost surface, and the needle-shaped nano structures may be formed on one surface or both surfaces of the pre-treating fiber. These needle-shaped nano structures may be formed by, for example, a process of etching at least one surface of the pre-treating fiber.

As described above, the needle-shape nano structure is a structure in which a plurality of protrusions in the form of nanoscale needle are formed, and the nano structure is formed not only on the outermost surface of the pre-treating fiber, but also at a specific inner surface portion from the outermost surface due to the morphological characteristics of fiber.

When the nano structure is thus formed not only on the outermost surface but also at an inner surface portion which is disposed at a predetermined depth from the outermost surface, the inner surface portion is safe from wear and tear, so that the aging effect does not substantially occur, and therefore, super-hydrophobic fiber, in which super-hydrophobic characteristics are maintained for a long period of time, may be obtained.

In general, the hydrophobic surface is formed by a method of coating a material having a low surface energy. However, when the method is adopted, hydrophobic characteristics may easily disappear due to peeling-off of the coated material or contamination by foreign substances and the like, and this effect refers to an aging effect. In other words, as time elapses, due to the aging effect that hydrophobic characteristics imparted to a fiber gradually disappear, it is difficult for the fiber to steadily maintain hydrophobic or super-hydrophobic characteristics. However, in the case of a fiber in which the needle-shaped nano structure is formed on the surface, the nano structure is formed not only on the outermost surface of the fiber, and due to the characteristics of woven form of the fiber, a reactive gas penetrates each fiber yarn at the time of etching treatment and as a result, needle-shaped nano structures are formed also at the inner surface portion which is about 100 to 200 μm deep, and therefore, the aging effect may be substantially prevented from occurring. For example, even though the nano structure of the outermost surface is structurally lost due to friction and the like, another nano structure is present at the inner surface portion which is safe from wear and tear and super-hydrophobic characteristics may be maintained for this reason, and therefore, the structural durability is excellent, and thus, super-hydrophobicity may be maintained for a long period of time.

The material for the hydrophobic fiber may be unwoven fabric, fabric, or knit. First, the fiber may be applied as long as the fiber is a polymer fiber which is easily etched, a carbon-containing polymer may be advantageous, and examples of the polymer include polyester-based, polyacryl-based, polyurethane-based, and polypropylene-based polymer fibers. Examples of specifically applicable polymer fiber include fiber including polyester, polyurethane, polyamide, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, acrylonitrile, polypropylene, or polyacryl, and the like, but the polymer fiber is not limited thereto.

For the polymer fiber, as long as the polymer fiber may easily form a nano structure, and will be used in a fiber product which requires super-hydrophic processes, super-hydrophobic fiber may be prepared by a method including forming the needle-shaped nano structure, and forming a coating layer and then may be applied, and be applicable to various fiber products. Examples of the applicable fiber product include clothing, a bag, an umbrella, a tent, a raincoat, shoes, a cap, a knapsack, a swimsuit, a banner, and the like.

The coating layer formed on the nano-needle fiber may have a thickness of 5 to 100 nm. When the thickness of the coating layer is 5 nm or less, the coating layer is so thin that additional hydrophobic characteristics may not be properly imparted and durability may deteriorate, and when the thickness of the coating layer exceeds 100 nm, each gap between the needle-shaped nano structures may be all filled with a coating material, so that super-hydrophobic characteristics due to the formation of the nano structure may deteriorate.

The hydrophobic material may be, for example, one selected from the group consisting of hexamethyldisiloxane (HMDSO), molybdenum disulfide (MoS₂), boron nitride (BN), polytetra fluoroethylene (PTFE), and a combination thereof, and it is also possible to use a diamond like carbon (DLC) material, or a material obtained by subjecting the aforementioned material to fluorization treatment. The aforementioned materials have high strength and excellent friction resistance, and thus may further enhance durability of the super-hydrophobic surface. It is preferred that as the hydrophobic material, hexamethyldisiloxane is applied.

The super-hydrophobic fiber may have a contact angle of 150 degree or more with pure water, and a sliding angle of 3 degree or less, preferably 2 degree or less with pure water. Here, the contact angle with pure water means an angle between a surface at the inner side of a liquid and a surface of a solid when a liquid drop of water containing no impurity, that is, water treated with an ion exchange resin is brought into contact with the solid, and the sliding angle with pure water means an angle between a tilted solid and a horizontal surface when a liquid drop of the water containing no impurity begins to tilt the solid while being in contact with the solid, and then begins to slide down.

When the super-hydrophobic fiber has the contact angle and the sliding angle within the aforementioned ranges, the surface of the fiber is super-hydrophobic, so that the fiber is not substantially wet even though the fiber is in contact with water, and slightly contaminated or seldom contaminated even though the fiber is in contact with a contaminant, and even though the contaminant or water is contact with the super-hydrophobic fiber, the contaminant or water is easily desorbed, and as a result, the fiber remains for a long period of time not being wet with water or not contaminated.

The fiber having these characteristics may be used for an umbrella, a raincoat, outdoor clothing (mountain-climbing clothes, ski clothes, and the like), shoes, a cap, a swimsuit, a bag, a knapsack and the like, thereby providing a functional fiber product having characteristics that the fiber is not wet with water, or is not easily contaminated.

A method for fabricating super-hydrophobic fiber according to another exemplary embodiment of the present disclosure includes: a preparation step of preparing a pre-treating fiber to be subjected to super-hydrophobic treatment; an etching step of etching an outermost surface of the pre-treating fiber and an inner surface portion which is 100 μm, preferably 150 μm, and more preferably 200 μm deep from the outermost surface to fabricate a nano-needle fiber having a surface on which needle-shaped nano structures are formed; and a coating step of forming a coating layer containing a hydrophobic material on the surface on which nano structures of the fiber are formed. FIG. 1 is a conceptual view describing an example of the method of fabricating super-hydrophobic fiber of the present disclosure step by step, and illustrates a pre-treating fiber, a (dry etching-treated) nano-needle fiber, and a (hydrophobically coated) super-hydrophobic fiber, in order from the top down.

Since the explanation for the raw material for the fiber, the hydrophobic material, the coating layer containing the hydrophobic material, the needle-shaped nano structure, and characteristics and advantages of the super-hydrophobic fiber, and the like is identical to that as described above, the description thereof will be omitted.

The etching step may be a step of etching an outermost surface of the pre-treating fiber and an inner surface portion which is about 100 μm to 200 μm deep from the outermost surface by one or more etching methods to form needle-shaped nano structures on the outermost surface and at the inner surface portion. FIG. 1 illustrates etching only one surface of the woven fiber, but the etching may be performed on one surface or both surfaces of the pre-treating fiber, and need-shape nano structures may be formed on the outermost surface and at the inner surface portion of fiber strands disposed on the etched surface.

The etching method may be performed by one method selected from the group consisting of plasma etching, reactive ion etching, ion-milling, electro discharge machining (EDM), and a combination thereof. Preferably, the etching may be performed by plasma etching.

Any plasma etching may be applied without limitation as long as the plasma etching is performed using plasma, and may be performed for 30 sec to 90 min by including a reactive gas, and any reactive gas may be applied as long as the reactive gas may be used for etching and does not excessively damage the fiber, and the reactive gas may be, for example, one selected from the group consisting of CF₄, CHF₃, C₂F₆, C₂Cl₂F₄, C₃F₈, C₄F₈, SF₆, O₂, and a mixture thereof.

With respect to the conditions under which the plasma etching is performed, the pressure may be 10 to 100 mTorr, the rf-power may be 100 to 400 W, the bias voltage may be 300 to 500 V, and time may be 30 sec to 90 min, preferably 5 min to 40 min. When the etching is performed with the numerical ranges of the conditions, a nano-shaped structure with an appropriate size may be formed on the fiber.

All of the etching methods are a dry etching method, and do not use an etchant, and therefore, the methods are a method which is environmentally-friendly due to low emission of hazardous materials, may reduce process costs due to the simple processes, and enables mass production due to ability to process a large area. The coating step may be a step of forming a coating layer containing a hydrophobic material by one coating method, and as illustrated in the bottom of FIG. 1, it is preferred that a method capable of forming a coating layer on the needle-shaped nano structures which are a nanoscale structural body is applied to the coating method. As the coating method, it is possible to apply, for example, plasma enhanced chemical vapor deposition (PECVD), atmospheric chemical vapor deposition (APCVD), low pressure chemical vapor deposition (LPCVD), metal-organic chemical vapor deposition (MOCVD), ultra-high vacuum chemical vapor deposition (UHCVD), or atomic layer deposition (ALD). Preferably, plasma enhanced chemical vapor deposition (PECVD) may be applied to the coating step, and when a coating layer is formed on the nano structure by this deposition method, it is possible to prepare super-hydrophobic fiber in which super-hydrophobicity is well maintained.

As the conditions under which the plasma chemical vapor deposition is performed, the pressure may be 5 to 30 mTorr, the rf-power may be 150 to 400 W, and the bias voltage may be 300 to 500 V, and only when the deposition is performed within the aforementioned range, a coating layer with an appropriate thickness may be formed, thereby fabricating super-hydrophobic fiber having a super-hydrophobic coating layer formed thereon while maintaining needle-like nano structures.

A fiber product including super-hydrophobic fiber according to still another exemplary embodiment of the present disclosure includes a fiber including: a nano-needle fiber having a surface including needle-shaped nano structures; and a coating layer disposed on the surface including needle-shaped nanostructures, and containing a hydrophobic material.

Since the explanation for the raw material for the fiber, the hydrophobic material, the coating layer containing the hydrophobic material, the needle-shaped nano structure, and characteristics and advantages of the super-hydrophobic fiber, and the like is identical to that as described above, the description thereof will be omitted.

The fiber product may be, for example, a raw fabric for a tent, a raw fabric for an umbrella, a raw fabric for shoes, a banner, a raw fabric for a cap, a raw fabric for a bag or a knapsack, clothing, or a combination thereof. The fiber product may be a raw fabric for an umbrella, and when the raw fabric for an umbrella is made of the super-hydrophobic fiber, a liquid drop such as a raindrop is rarely absorbed in the raw fabric, and as a result, the umbrella is not wet, and needs not be dried after the umbrella is used. Further, since an umbrella tray, a plastic bag for storing an umbrella and the like are not required for a rainy day any more, convenience of life in a rainy day may be further improved.

In addition to the umbrella, the fiber products fabricated by including the super-hydrophobic fiber as described above may remove inconvenience occurring and need for incidental auxiliary articles if the product are wet, and accordingly, social costs may be reduced, and the fiber products may also be applied to various fields.

Since the super-hydrophobic fiber of the present disclosure has such a large contact angle and such a small sliding angle that the fiber has a needle-shaped nano structure in which a liquid drop is not absorbed, and super-hydrophobicity may be maintained without an aging effect for a long period of time, durability is excellent, and super-hydrophobic characteristics may be maintained for a long period of time. In addition, the method for fabricating super-hydrophobic fiber of the present disclosure may be easily applied to the industry because the processes are simple, mass production may be achieved, and hazardous materials such as an etchant are not used.

Furthermore, the article including the super-hydrophobic fiber is an article in which a liquid drop is not absorbed at all and needs not be dried, and when the article is used as an umbrella or a raincoat in a rainy day, hygienically necessary incidental articles, such as an umbrella storage box and a plastic bag for storing an umbrella, are not required any more, and as a result, social costs may be reduced, and the articles may also be applied to various recreational articles in addition to this purpose.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments and together with the description serve to explain the principles of the disclosure.

In the drawings:

FIG. 1 is a conceptual view describing an example of the method of fabricating super-hydrophobic fiber of the present disclosure step by step, and illustrates a pre-treating fiber, a (dry etching-treated) nano-needle fiber, and a (hydrophobically coated) super-hydrophobic fiber, in order from the top down.

FIG. 2 is a low-magnification photograph of pre-treating fiber taken by scanning electron microscope (SEM).

FIG. 3 is intermediate-magnification and high-magnification photographs of pre-treating fiber taken by scanning electron microscope (SEM).

FIG. 4 is intermediate-magnification and high-magnification photographs of nano-needle fiber taken by scanning electron microscope (SEM).

FIG. 5 is photographs taken when a liquid drop is placed on the surface of the pre-treating fiber (left) and on the surface of super-hydrophobic fiber which is an exemplary embodiment of the present disclosure (right).

FIG. 6 is a graph showing the results obtained by measuring the contact angles of the pre-treating fiber and the super-hydrophobic fiber which is an exemplary embodiment of the present disclosure.

FIG. 7 is a graph showing the results obtained by measuring the contact angles and sliding angles of the super-hydrophobic fiber which is an exemplary embodiment of the present disclosure immediately after the fabrication and after elapse of 80 days after the fabrication.

DETAILED DESCRIPTION OF THE DISCLOSURE

Description will now be given in detail of the exemplary embodiments, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components will be provided with the same reference numbers, and description thereof will not be repeated.

Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings, such that those skilled in the art to which the present disclosure pertains can easily carry out the invention. However, the present disclosure can be implemented in various different forms, and is not limited to the exemplary embodiments described herein.

EXAMPLE. Fabrication of Hydrophobic Fiber Preparation Example 1. Fabrication of Nano-Needle Fiber

A polyester fabric was used as pre-treating fiber, and hexamethyldisiloxane was used as a hydrophobic material. First, the polyester fabric was etched for about 30 min using an ion-beam etching device by a plasma etching method (dry etching) using O₂ as a reactive gas under conditions of a pressure of 20 mTorr, an oxygen flow rate of 10 sccm, an RF-power of 250 W, and a bias voltage of 400V, thereby fabricating a nano-needle fiber having a surface including needle-shaped nano structures, as illustrated in the middle of FIG. 1.

Preparation Example 2. Fabrication of Super-Hydrophobic Fiber

Plasma enhanced chemical vapor deposition (PECVD) was used to perform a plasma treatment on the surface (on the surface of the nano-needle fiber) of needle-shaped nano structures in Preparation Example 1 for about 15 sec while hexamethyldisiloxane was allowed to flow at 10 sccm under conditions of a pressure of 10 mTorr, an RF-power of 250 W, and a bias voltage of 400 V, and a coating layer including hexamethyldisiloxane as a hydrophobic material was formed as illustrated in the bottom of FIG. 1, thereby fabricating super-hydrophobic fiber.

FIGS. 2 and 3 are photographs of the surface of the pre-treating fiber before the etching step was performed, taken at various magnifications by using a scanning electron microscope. It can be seen that the pre-treating fiber before the etching step was performed had a significantly smooth surface. However, FIG. 4 is photographs of the surface of the nano-needle fiber after the etching step was performed, taken by scanning electron microscope, and it can be confirmed that needle-shaped nano structures were formed on the surface of the nano-needle fiber.

Experimental Example. Evaluation of Super-Hydrophobic Fiber

1. Evaluated Physical Properties and Measurement Method

The contact angle of the super-hydrophobic fiber fabricated in the Example was measured using NRL Contact Angle Goniometer. The contact angle was measured by a method including: aligning the base line of the fiber, slightly dropping a liquid drop thereon, and then rotating a goniometer to read a measured angle. The contact angle measurement photograph was taken by using a GBX machine. Further, the sliding angle of the super-hydrophobic fiber was measured by using a high speed camera. The sliding angle was measured by a method including: aligning the base line of the fiber, slightly dropping a liquid drop thereon, and then reading an angle between the tilted fiber and the horizontal plane when the liquid drop began to flow while the fiber was slowly slanted, and the sliding angle measurement photograph was taken by using a high speed camera.

2. Evaluation of Wettability of Pre-Treating Fiber and Super-Hydrophobic Fiber

Referring to FIG. 5, it can be confirmed that a liquid drop was almost absorbed in the pre-treating fiber illustrated in the left photograph, whereas the liquid drop was scarcely absorbed in the super-hydrophobic fiber of the present disclosure illustrated in the right photograph while almost maintaining a spherical shape. In addition, referring to the graph in FIG. 6, it can be confirmed that the pre-treating fiber had a contact angle of about 50 degree as observed in the left photograph of FIG. 5, whereas the fiber had a contact angle of about 150 degree, which is a significantly large value after the method of the present disclosure was performed.

3. Evaluation of Durability of Super-Hydrophobic Fiber (Evaluation of Aging Effect)

The contact angle and sliding angle of the super-hydrophobic fiber were measured immediately after the method of the present disclosure had been performed, and the contact angle and sliding angle of the super-hydrophobic fiber were measured after 80 days elapsed. The device and the method, which are the same as in the device of measuring a contact angle, were applied to the measurement of the sliding angle. As a result, referring to FIG. 7, when comparing the case immediately after the method had been performed with the case after 80 days elapsed, it can be seen that the sliding angle was slightly increased, but the result of the contact angle was almost the same as the initial result, and through this, it can be confirmed that the super-hydrophobic fiber of the present disclosure is also excellent in durability.

While preferred embodiments of the present disclosure have been described in detail, it is to be understood that the scope of the present disclosure is not limited thereto, and various modifications and variations made by those skilled in the art using basic concepts of the present disclosure defined in the following claims also fall within the scope of the present disclosure.

The foregoing embodiments and advantages are merely exemplary and are not to be considered as limiting the present disclosure. The present teachings can be readily applied to other types of apparatuses. This description is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments.

As the present features may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be considered broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims. 

What is claimed is:
 1. A super-hydrophobic fiber comprising: a nano-needle fiber having a surface comprising needle-shaped nano structures; and a coating layer disposed on the surface comprising needle-shaped nano structures; wherein the needle shaped nano structure has a height of 50 to 150 nm and a width of 5 to 20 nm, and the surface comprising needle-shaped nano structures comprises 2 million to 4 million needle-shaped nanostructures per 1 mm² of an area.
 2. The super-hydrophobic fiber of claim 1, wherein the needle-shaped nano structures are formed on the outermost surface of a pre-treating fiber and at the inner surface portion which is up to 100 μm deep from the outermost surface.
 3. The super-hydrophobic fiber of claim 1, wherein the super-hydrophobic fiber is one material selected from the group consisting of polyester, polyurethane, polyamide, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, acrylonitrile, polypropylene, polyacryl, and a combination thereof.
 4. The super-hydrophobic fiber of claim 1, wherein the coating layer has a thickness of 5 to 100 nm.
 5. The super-hydrophobic fiber of claim 1, wherein the hydrophobic material is one selected from the group consisting of hexamethyldisiloxane (HMDSO), molybdenum disulfide (MoS₂), boron nitride (BN), polytetra fluoroethylene (PTFE), fluorinated diamond like carbon (F-DLC), and a combination thereof.
 6. The super-hydrophobic fiber of claim 1, wherein the super-hydrophobic fiber has a contact angle of 150 degree or more with pure water.
 7. The super-hydrophobic fiber of claim 1, wherein the super-hydrophobic fiber has a sliding angle of 3 degree or less.
 8. A method for fabricating super-hydrophobic fiber, the method comprising: a preparation step of preparing a pre-treating fiber to be subjected to super-hydrophobic treatment; an etching step of etching an outermost surface of the pre-treating fiber and an inner surface portion which is 100 μm deep from the outermost surface to fabricate a nano-needle fiber having a surface on which needle-shaped nano structures are formed; and a coating step of forming a coating layer containing a hydrophobic material on the surface on which nano structures of the fiber are formed.
 9. The method of claim 8, wherein he etching step is one method selected from the group consisting of plasma etching, reactive ion etching, ion-milling, electro discharge machining (EDM), and a combination thereof.
 10. The method of claim 9, wherein the plasma etching is performed for 30 sec to 90 min while a reactive gas is included, and the reactive gas is one selected from the group consisting of CF₄, CHF₃, C₂F₆, C₂Cl₂F₄, C₃F₈, C₄F₈, SF₆, O₂, and a mixture thereof.
 11. The method of claim 10, wherein the plasma etching is performed under conditions of a pressure of 10 to 100 mTorr, an rf-power of 100 to 400 W, and a bias voltage of 300 to 500 V for 5 min to 40 min.
 12. The method of claim 8, wherein in the coating step, a coating layer containing a hydrophobic material is formed by one selected from the group consisting of Plasma Enhanced Chemical Vapor Deposition (PECVD), Atmospheric Chemical Vapor Deposition (APCVD), Low Pressure Chemical Vapor Deposition (LPCVD), Metal-Organic Chemical Vapor Deposition (MOCVD), Ultra-high vacuum Chemical Vapor Deposition (UHCVD), Atomic Layer Deposition (ALD), and a combination thereof.
 13. The method of claim 8, wherein the coating step is performed by plasma enhanced chemical vapor deposition (PECVD), and is performed under conditions of a pressure of 5 to 30 mTorr, an rf-power of 150 to 400 W, and a bias voltage of 300 to 500 V.
 14. The method of claim 8, wherein the needle-shaped nano structure has a height of 50 to 150 nm and a width of 5 to 20 nm, and comprises 2 million to 4 million needles per 1 mm² of a surface area of the fiber.
 15. The method of claim 8, wherein the fiber is one selected from the group consisting of polyester, polyurethane, polyamide, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, acrylonitrile, polypropylene, polyacryl, and a combination thereof.
 16. The method of claim 8, wherein the hydrophobic material is one selected from the group consisting of hexamethyldisiloxane (HMDSO), molybdenum disulfide (MoS₂), boron nitride (BN), polytetra fluoroethylene (PTFE), fluorinated diamond like carbon (F-DLC), and a combination thereof.
 17. A fiber product comprising: a nano-needle fiber having a surface comprising needle-shaped nano structures; and a coating layer disposed on the surface comprising needle-shaped nanostructures, and containing a hydrophobic material; wherein the needle-shaped nano structure has a height of 50 to 150 nm and a width of 5 to 20 nm, and comprises 2 million to 4 million needles per 1 mm² of a surface area of the fiber.
 18. The fiber product of claim 17, wherein the fiber product is one selected from the group consisting of a tent, an umbrella, shoes, a banner, a cap, a bag, a knapsack, and clothes. 